Mimicry: Please help me understand how

Mimicry, as a form of camouflage, is quite common among various species of animals. Take, for instance, the numerous species of spiders, beetles, and butterfly/moth caterpillars etc., that mimic bird droppings as an avoidance strategy to predation. Any species that employs this strategy must have had some ancestral form that did not resemble bird droppings in any way. Given that starting point, how did bird dropping mimicry evolve?, considering that a random mutation that led to individuals appearing EVER SO SLIGHTLY like bird droppings would not have been significant enough (in my mind) to result in differential survivability leading to differential reproductive success. How can appearing EVER SO SLIGHTLY like bird droppings be advantageous? And then to assume that this happens over and over again to result in a form that is virtually indistinguishable from a bird dropping, seems to be a bit of a stretch. Your thoughts?Thanks

Chiroptera gave a plug to this topic at the Considerations of topic promotions from the Proposed New Topics forum.There is an existing topic on this, Mimicry and neodarwinism. It is at message 187 and was active up to a couple of months ago.I am not rejecting this new "Proposed New Topic" (PNT), but all may wish to consider the above cited. If that topic doesn't do the job, then this one can be promoted.Lampropeltis can comment in this topic. Others can comment in the "Considerations..." topic.On hold for now.AdminnemooseusEdited by Adminnemooseus, : Fix typo in subtitle.

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From the General Discussion Of Moderation Procedures 11.0 topic (it should have been in the Considerations of topic promotions from the "Proposed New Topics" forum topic). Yea, I noticed that. Sounds like a good reason to close the older topic and promote this one.Stand by.AdminnemooseusEdited by Adminnemooseus, : Fixing "signature" links.

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Thread moved here from the Proposed New Topics forum.

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How can appearing EVER SO SLIGHTLY like bird droppings be advantageous?

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Although at this stage the creature looks nothing like bird droppings yet, it will look ever so slightly LESS like the original form that the predator is hunting for, which will increase its survivability.

There is a useful analogy to this, and it is this joke:

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Two friends went camping and were sleeping in a tent when one heard a rustling sound. He woke up and recognized the odor and growls as those of a bear. He woke up his friend and told him that there was a bear on the loose in the campsite. Without saying a word the freshly-woken friend began to put on his running sneakers. Upon seeing this the other friend started laughing and incredulously asked, "You're not planning on outrunning that bear, are you?!? He'll chase you down!" The other friend continued to be silent and put on his other shoe. The friend again asked, "You do understand that you cannot outrun a bear, don't you?!?" At this point the other friend finished tying his running shoes sat up and with a gleam in his eye said to his interrogating friend, "I know that I cannot outrun a bear. All I have to do is outrun you!" and took off.

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The insect or spider doesn't have to hide from the bird completely - it just has to hide slightly better than everyone else.Remember that a bird may only get is a fleeting glance, and no bird has the big brain that allow us humans to recognise images (ever see a bird attack its own reflection?), and that these birds don't have a minute to sit in front of a picture to scrutinize it.Consider also that this is hardly likely to be a disadvantage to the organism - it will be neutral at worst. 0.001% less of a chance of being eaten by a bird is still better than no change at all. So, because there is not real selection pressure acting against it, the tiny selection pressure acting for it can still make a difference. And, the more difference it makes, the more it increases the selection pressure, hence snowballing the effect until eventually the species looks as close to bird-droppings as it's morphology will allow.

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This answer was already suggested by Richard Dawkins in The Blind Watchmaker (and hinted at by another poster).A bug that looks only ever so slightly more like a bird dropping or twig or leaf or may not fool you (or a bird or another, bigger bug) if you happen to look directly at it in broad daylight.But out of the corner of your eye, it might just be enough to escape your attention. So, assuming that some bugs are first noticed by birds out of the corners of their eyes, slightly fewer bugs that are ever so slightly harder to detect will be eaten than "normal" bugs. Also, at twilight, when light levels are lower and it's harder to see anything, being ever so slightly harder to see may be just enough to avoid being eaten.

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Q: If science doesn't know where this comes from, then couldn't it be God's doing?A: The only difference between that kind of thinking and the stereotype of the savage who thinks the Great White Hunter is a God because he doesn't know how the hunter's cigarette lighter works is that the savage has an excuse for his ignorance. -- jhuger

Interesting question.First of all, in general, camouflage and mimicry always works better at a distance. Any slight improvement would reduce the minimum distance at which the camouflage is effective.Take, for example, soldiers' khakis. They don't make a soldier look very vegetation, but at a distance they do offer concealment.In the case of bird-dropping mimics, being dull-colored and speckled is already a form of camouflage. (Speckles break up the three-dimensional form of an object, making it harder to see: again, the priciple is applied in military khaki.) If a particular variation of such markings also has some tendency to make the creature look like bird-droppings to any bird that does spot the caterpillar, that's obviously an advantageous trait.Welcome to the forums.

I have adressed the issue in the thread "Mimicry and neodarwinism". Dawkins and some contibutors here propose small gradual steps as explanation. In the case when one butterfly resembles some other unpalatable butterfly (Batesian or Mullerian mimicry) such explanation is not accepted in scientific community as far as I can judge. Dawkins in not scientist strictly speaking. I have already quoted Nijhout who have made many researches in the area of butterfly mimimicry and who wrote:
"Initial step in the evolution of mimicry is likely to have been due to a genetic effect of large magnitude".It is necessary that first step towards model is great in order to deceive predator. Predators sometimes taste also unpalatable species.The problem of mimicry is much more complicated as it may seems. Very often mimics outnumber models. Sometimes we observe polymorphic mimicry - some races of the same butterly species mimic different unpalatable species but some races of it do not. So we have mimic and non-mimic of the same species and both thrive very well.On the meadow you can observe bright palatable and bright unpalatable butterflies as well as some mimic species. All of them thrive and live on the same area. Obviously in such case one have to ask question how natural selection works in reality.I quoted also Punnet and Goldschmdt, both prominent scientists, who claimed that mimicry arouse suddenly, by saltus.Other, non-darwinian explanation are due some kind of "synchronicity".Anyway gradual steps seems to be unplausible explanation in the case of Mullerian mimicry, when one unpalatable butterfly mimics another unpalatable species. In that case small change would shift off resemblance from aposematic coloration of own species. And yet it would not give fully protection of coloration of the model species. Again we should explain the fact that on the same area thrive Mullerian mimics and also palatable non-mimic species as well. I can hardly imagine what kind of natural selection took effect on the mimic species and very often close related species on the same area was somehow ovelooked by it.Edited by AdminWounded, : Added link to older thread.

Further to that Dawkins reminds states: If the selection pressure to be a little less conspicuous to birds is so slight as to be unnoticeable to biologists...it could still result in quick and radical changes.

Since the last thread was closed and this one opened due to, to paraphrase: MartinV being all over it, I warn people to do their best to not rise to the posts made by MartinV, since that will surely guarantee the same state of affairs. MartinV's views on mimicry can be found at that thread, and perhaps it can be reopened once this one winds down so that MartinV can continue defending his position.MartinV, whatever your opinion on this, might I politely ask that you allow this thread to develop with as little input as possible - even if it is only to allow our new member to get noticed. Judging by how much debate your views put forward, our new member might be overwhelmed.Nothing hard and fast being demanded here, just that all members bare the above in mind. We can play it by ear for the time being. If it becomes a problem, I, or another moderator, will be stepping forward to take appropriate action (warnings, closures, suspensions etc etc).Thank you.

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Ah, Ledyard Stebbins. I remember his book, Darwin to DNA, Molecules to Humanity. I got this book free when I subscribed to Scientific American in 1982 or 1983, shortly after I dumped creationism. I still had a lot of questions about evolution at that time, and this book was instrumental for a key insight that I didn't really understand before.

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Q: If science doesn't know where this comes from, then couldn't it be God's doing?A: The only difference between that kind of thinking and the stereotype of the savage who thinks the Great White Hunter is a God because he doesn't know how the hunter's cigarette lighter works is that the savage has an excuse for his ignorance. -- jhuger

There was no response 10 days so I feel free to add something. According neo-darwinsim wasps have aposemtic coloration to deter predators. Butterfly Aegeria apiformis look and buzz like a wasp. One would thing that the butterfly has some survival advantage looking like a wasp. But probably no scientist has made a research to prove it. Wasps have many bird's predators who eat them.One of them is bird Merops apiaster living in Europe - Bee eater:

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Just as the name suggests, bee-eaters predominantly eat insects, especially bees, wasps and hornets, which are caught in the air by sorties from an open perch.

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European bee-eater - Wikipediaor curl-crested jay (Cyanocorax cristatellus):

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These observations suggest that predation by birds could play an important role in the dynamics of social wasp populations.

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Bird predation on nest of a social wasp in Brazilian cerradoIt is only neo-darwinian pressuposition that a butterfly mimicing wasps are protected having wasp coloration. Probably no serious research has been done yet.Edited by MartinV, : No reason given.

You would be incorrect in your guesses. Serious research has been done in the field.For example:In 2001 Dr. David W. Pfennig (UNC-Chapel Hill), Dr. Karin S. Pfennig (UT Austin's College of Natural Sciences), and William Harcombe (UNC-Chapel Hill undergraduate) studied the Scarlet King Snake (Lampropeltis triangulum) a non-poisonous snake that mimics the poisonous species Eastern Coral Snake (Micrurus fulvius).They designed an experiment placing artificial King Snakes and an artificial brown snake as a control within the region and outside of the region that the poisonous snakes are found. The experiment was to see if mimicing the poisonous snake reduced the amount of attacks in the region where the two snake species are found together.[1]They found that within the region where the poisonous snake was found 84% more attacks where made on the control group (brown) than the 16% of attacks on the mimicing King Snake. Outside the area however 83% of the attacks where made on the King Snake while the control only suffered 17% of the attacks.[2]This experiment does show that the mimicing King snake does get attacked less often within the region where Coral snakes are found. It also shows that outside this region such bright colors can be a disadvantage as it suffered not an equal amount of attacks as the control but more attacks.[1]Campbell, N.A., Reece, J.B. 2005. Biology, seventh ed. Pearson Education, Inc., pp.22
[2]Campbell, N.A., Reece, J.B. 2005. Biology, seventh ed. Pearson Education, Inc., pp.23

Thank you for your response. I would appeciate if the experiment was accessible on-line for closer examination. I have 2 points:1) Genera Micurus (according Robert Mertens 1954) in Brazil is very poisonous and no predator survive its biting. Consequently no one can remember the species as dangerous.2) I don't know if the species are diurnal or nocturnal. At least Scarlet snake you mentioned as mimic is nocturnal species. I do not see what kind of natural selection is acting to diurnal species to look like bright colored poisonous model.

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The Florida scarlet snake is locally abundant, but rarely seen due to its secretive nature. It lives mostly underground, in or under logs, or burrowed under tree bark. It is nocturnal and sometimes seen after dark crossing roads.

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Cemophora coccinea - Scarlet snake -- Discover Life